PROJECT ABSTRACT This proposed Phase I SBIR project will result in development and testing of a prototype of Virtual Support System (VSS), a mobile health (mHealth), video-based system that provides support to young Black men who have sex with men (YBMSM) across the entire HIV care continuum. There are currently 1.1 million people living with HIV in the United States, and among MSM nationally, Black MSM had the highest number of HIV diagnoses in 2016. Engagement in care is often thought of as a continuum including 1) HIV diagnosis, 2) linkage to care, 3) retention in care, 4) HIV antiretroviral therapy (ART) initiation, and 5) viral suppression, and YBMSM experience severe disparities across the HIV care continuum, compared to both older Black MSM and young White and Latino MSM. VSS addresses many challenges that lead to poor treatment initiation, adherence, and retention outcomes. It takes a holistic approach, tailored specifically for YBMSM, to improve well-being and mental health through providing video-based support, information on demand, and facilitating access to local resources within a simple-to-follow user interface. We hypothesize that VSS, created with intensive community collaboration, will optimize well-being and health outcomes for YBMSM ages 18-29 who are living with HIV, and reduce disparities along the HIV care continuum for this population. This new intervention will enhance the ability of HIV service organizations nationwide to ensure optimal HIV care for YBMSM clients, as it can be easily integrated into their existing linkage and case management services. Several HIV service organizations have expressed a need for VSS and will support the project as collaborators. There are three specific aims to our proposal. AIM 1: Conduct qualitative research, including focus groups with YBMSM living with HIV and interviews with their service providers to inform the development of VSS. AIM 2: Create prototypes for VSS using the formative research results from Aim 1 and conduct prototype testing with YBMSM living with HIV and service providers. AIM 3: Conduct prototype usability testing in an online survey of a large, diverse sample of YBMSM living with HIV to maximize program utility and uptake, and refine the prototype as needed. Phase I will involve formative research, then developing, testing, and refining a VSS product prototype. This 6- month timeline is closely aligned with other fast-paced, successful projects that Dr. Montoya and the team at Sentient Research regularly plan and execute. After building out the program and evaluating it using a randomized controlled trial in Phase II, VSS will ultimately have rapid, wide-scale, and sustainable impact. Because VSS is app-based, it can be easily adapted and scaled up for organizations operating at the local, regional, or national level, and can be used in a wide range of settings. The program could also be used in resource-limited and rural settings, areas for which mHealth approaches are promising.